Regulatory T cells (Tregs) are a subset of CD4+ T cells that suppress immune responses and are essential mediators of self-tolerance and immune homeostasis (Sakaguchi, et al., Cell, 133, 775-787 (2008)). Depletion or inactivation of Tregs results in the development of severe autoimmunity (Sakaguchi, et al., J. Immunol., 155, 1151-1164 (1995)), and their accumulation inhibits anti-tumor immunity (Dannull, et al., The Journal of clinical investigation, 115, 3623-3633 (2005)). Tregs are characterized by Foxp3 expression, a transcription factor belonging to the Forkehead Box family of transcription factors. The Foxp3 is a master regulator of Tregs, as it is necessary for their development and function (Hori, Science, 299, 1057-1061 (2003); Fontenot, et al., Nat Immunol., 4(4):330-6 (2003). Epub 2003 Mar. 3; Khattri, et al., Nat Immunol., 4(4):337-42 (2003). Epub 2003 Mar. 3)).
There are two major types of Tregs: thymus-derived Tregs (or natural Tregs (nTregs)) that constitute 5-10% of the total peripheral CD4+ T cells, and peripheral TGFβ-induced Tregs (iTregs). Both types are shown to have immunosuppressive properties mediated via several processes that involve immunosuppressive soluble factors or cell contact (Bluestone, et al., Nat Rev Immunol, 3, 253-257 (2003); Glisic, et al., Cell and Tissue Research, 339, 585-595 (2010); Hori, Science, 299, 1057-1061 (2003); Sakaguchi, Cell, 101, 455-458 (2000); Sakagushi, et al., Curr. Top Microbiol. Immunol., 305, 51-66 (2006); Sakagushi, et al., Immunol., Rev., 212, 8-27 (2006); (Schmidt, et al., Front Immunol., 3:51 (2012)). However, the molecular mechanisms by which nTreg and iTreg develop and then exhibit non-redundant roles to suppress the immunity are not fully understood (Dipica, et al., Immunity, 35(1):109-122 (2011)).
PI3K-Akt signaling affects many processes and is central to many signaling pathways. Akt phosphorylation and kinase activity are induced by PI3K activation, which is, in turn, induced by several growth factor receptors, TCR, CD28, and IL-2R, among many others (Parry, et al., Trends in Immunology, 28, 161-168 (2007)). In mammals, there are three Akt isoforms, namely Akt1, Akt2, and Akt3, encoded by three independent genes. In vitro, these isoforms appear to have redundant functions, as different extracellular inputs can induce similar Akt signaling patterns (Franke, Science 1, pe29-(2008)). However, isoform-specific knockouts show unique features and their involvement in diseases and physiological conditions is different (Boland, et al., American Journal of Human Genetics, 81, 292-303 (2007); DeBosch, et al., J. Biol. Chem, 281, 32841-32851 (2006); Emamian, et al., Nat Genet, 36, 131-137 (2004); Garofalo, et al., The Journal of clinical investigation, 112, 197-208 (2003); George, et al., Science, 304, 1325-1328 (2004); Nakatani, et al., The Journal of Biological Chemistry, 274, 21528-21532 (1999); Tschopp, et al., Development (Cambridge, England), 132, 2943-2954 (2005); Yang, et al., J. Biol. Chem., 278, 32124-32131 (2003)).
Studies have shown that Akt1 and Akt2 can negatively regulate the transcriptional signature of Treg, thereby selectively affecting Treg lineage differentiation (Sauer, et al., Proceedings of the National Academy of Sciences, 105, 7797-7802 (2008a)). Additionally, although it was shown that inhibition of Akt1 and Akt2 isoforms increase Foxp3 expression in TGFβ induced iTregs (Sauer, et al., Proc. Natl. Acad. Sci. USA, 105, 7797-7802 (2008b)), the mechanism remained unclear. Another finding shows that deletion of Akt2 resulted in defective iTh17 cell differentiation but preserved nTh17 cell development (Kim, et al., Nat Immunol., 14(6):611-8 (2013) Epub 2013 May 5). Further, Akt3 is also expressed in immune cells and the spinal cord of Akt3 knockout mice have decreased numbers of Foxp3+ regulatory T cells compared with wild type mice (Tsiperson, et al., J Immunol., 190(4):1528-39 (2013) Epub 2013 Jan. 18)). Thus, although some studies have examined the relevance of Akt isoform expression on T cell biology (Carson, et al., Annals of the New York Academy of Sciences, 1103, 167-178 (2007), Crellin, et al., Blood, 109, 2014-2022 (2007a); Crellin, et al., Journal of Immunological Methods, 324, 92-104 (2007b); Haxhinasto, J. Exp. Med., 205, 565-574 (2008); Li, et al., Blood, 106, 3068-3073 (2005); Patton, et al., Biochem. Soc. Trans., 35, 167-171 (2007); Patton, et al., J. Immunology 177, 6598-6602 (2006); Sauer, et al., Proc. Natl. Acad. Sci. USA, 105, 7797-7802 (2008b); Walsh, et al., J. Clin. Invest., 116, 2521-2531. (2006)), the roles that Akt isoforms play in Treg function and induction was not clear.
Therefore, there remains a need to identify the molecular pathways underlying Treg activity, and to develop therapeutics for targeting the pathways to modulate Treg activity.
It is an object of the invention to provide a molecular pathway for modulating the development of nTregs and the polarization of iTregs, and to provide compositions for modulating the pathway.
It is an object of the invention to provide methods of using the compositions to modulate nTregs and iTregs in subjects in need therefore.